1. Field of the Invention
The present invention relates to patient interface devices for communicating a flow of gas with an airway of a user, and, in particular, to a patient interface device including a bladder assembly structured to provide automatic adjustment of nose bridge pressure.
2. Description of the Related Art
There are numerous situations where it is necessary or desirable to deliver a flow of breathing gas non-invasively to the airway of a patient, i.e., without intubating the patient or surgically inserting a tracheal tube in their esophagus. For example, it is known to ventilate a patient using a technique known as non-invasive ventilation. It is also known to deliver continuous positive airway pressure (CPAP) or variable airway pressure, which varies with the patient's respiratory cycle, to treat a medical disorder, such as sleep apnea syndrome, in particular, obstructive sleep apnea (OSA), or congestive heart failure.
Non-invasive ventilation and pressure support therapies involve the placement of a patient interface device including a mask component on the face of a patient. The mask component may be, without limitation, a nasal mask that covers the patient's nose, a nasal cushion having nasal prongs that are received within the patient's nares, a nasal/oral mask that covers the patient's nose and mouth, or a full face mask that covers the patient's face. The patient interface device interfaces the ventilator or pressure support device with the airway of the patient, so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient.
Typical designs for the mask component of a patient interface device include a faceplate having a cushion attached thereto which seals around the nose and sometimes the mouth of the patient. The faceplate is often connected to a forehead support having a forehead pad which provides an additional point to anchor the mask on the face of the patient. The faceplate and/or faceplate/forehead support arrangement is typically strapped to the head of the patient using a headgear component comprised of upper straps connected to the faceplate or forehead support and lower straps connected to the faceplate. The upper straps are typically tightened or loosened to adjust the fit of the upper portion of the cushion with respect to the patient's face (particularly around the nose bridge). The lower straps are typically tightened or loosened to adjust the fit of the remainder of the cushion (especially the lower portion) with respect to the patient's face.
Because such patient interface devices are typically worn for an extended period of time, it is important for the headgear component to maintain the mask component of the device in a tight enough seal against the patient's face without causing discomfort. As mentioned above, the upper straps are typically tightened in order to move the upper portion of the mask cushion into the nose bridge. If significant adjustment is required, this may require severe tightening of the upper headgear straps. In prior art designs, this strategy, while producing the desired effect of improving the cushion fit around the nose bridge, also produces the unwanted side effect of generating uncomfortable pressure on portions of the patients head, such as the patient's forehead (possibly resulting in red mark formation on the skin).